This proposal requests salary support to protect the applicant's time to focus on the proposed studies, and associated career development in sickle cell disease (SCO) research. The applicant's long-term goal is to develop and sustain an internationally recognized research laboratory focused on unraveling adhesive mechanisms that regulate blood cell-endothelial cell interactions and endothelial dysfunction in SCO. Endothelial cells fulfill a central role in the response to inflammation by controlling the number of circulating monocytes recruited to interstitial tissue compartments. Monocyte transendothelial migration is enhanced by sickle erythrocytes, which adhere tightly to endothelial cells and up-regulate expression of multiple adhesion molecules. A single nucleotide polymorphism in the promoter of the gene for the major monocyte chemoattractant CCL2 is an independent predictor of morbidity in SCO, highlighting excessive monocyte recruitment as a contributing factor in the pathogenesis of SCO. Despite this significance, the identity of adhesion molecules and cognate mechanisms responsible for regulating transendothelial monocyte migration in the lung, and the impact sickle erythrocytes have on this process and lung endothelial barrier function, remains poorly understood and is therefore the focus of this application. Activated leukocyte cell adhesion molecule (ALCAM) is expressed by activated monocytes. The applicant's laboratory has identified ALCAM at intercellular junctions in pulmonary microvascular endothelial cells, and showed that it is required for transmigration of monocytes across cultured pulmonary microvascular endothelial cells. The proposed study will enhance the applicant's research skills in a number of areas in vascular biology including creation of chimeric mice, and allow the applicant to extend the scope of a current NIH R01 award. Equally importantly, this K02 award will allow the applicant transition back into SCO research. These career objectives will be achieved by completing three specific aims namely, 1) ALCAM is an essential component of the adherens junction in lung endothelial cells, 2) Recruitment of activated monocytes into the lung is regulated by homotypic ALCAM adhesion, and 3) Develop a live imaging system to monitor monocyte transendothelial migration, and investigate the impact of sickle erythrocytes on lung endothelial barrier functions. The protected time, enhancement of research skills and reverse transition into SCO research will equip the applicant to pursue vascular wall biology research in SCO well into the future. The results of this career award will help the applicant generate chimeric SCO mice with the type of lung injury typically found in patients with SCO. Thus, the significance of this proposal extends beyond the immediate goal of unraveling the fundamental cause of pulmonary endothelial inflammation in SCO, to developing variants of the SCO mouse model that can be used to develop rationale therapy for pulmonary complications in SCD. (End of Abstract)